1. Field of the Invention
The present invention relates to a battery module case in which a plurality of battery cells are stored.
2. Description of the Related Art
Electric vehicles have been considered more and more to reduce exhaust gas discharged from vehicles to the environment. Since an electric vehicle obtains its driving force by driving electric motors, battery cells which constitute an electric power source are installed in the vehicle. In the electric vehicle, since a large number of battery cells needs to installed in a limited space, a plurality of battery cells are stacked to constitute a battery module, and a large number of battery modules are stored in a battery case disposed underneath a floor of the vehicle. A plurality of battery cells is stored in a stacked state in a battery module case.
The lives of battery cells can be maintained long while maintaining a high battery efficiency by holding the battery cells in a predetermined temperature range. In addition, in order to eliminate any variation in battery performance, it is required to maintain the temperatures of many battery cells uniform by suppressing the occurrence of a difference in temperature therebetween. Because of this, there have been proposed various art for cooling battery cells uniformly (for example, refer to JP-A-2000-67934 and JP-A-2004-311157).
Related art disclosed in JP-A-2000-67934 is art in which a guide is provided at an inducing portion of a cooling fluid passage of a battery module so that the cooling fluid is allowed to flow uniformly throughout the fluid passage so as to attain a uniform dissipation of heat of the battery module. In addition, related art disclosed in JP-A-2004-311157 is art in which a plurality of battery modules is disposed in such a manner that their terminals are made to confront each other and a cooling fluid is divided to flow into the battery modules from a cooling fluid passage where the terminals are made to confront each other, so as to cool the plurality of battery modules uniformly.
According to the related art, the battery cells which are stacked in the battery modules can be cooled uniformly on the basis of battery module by battery module. However, since in the battery module, a plurality of battery cells is stored in a battery module case, according to the related art, although a plurality of battery modules can be cooled uniformly, there is caused a variation in cooling of the plurality of battery cells stacked in the single battery module.
Namely, the battery module is made up of a case which has face plates on both sides of a frame element and a plurality of battery cells stored in the case, and the plurality of battery cells is stacked between the face plates. In addition, a plurality of battery modules like the battery module described above is disposed in a battery case, so as to constitute, for example, a power source of an electric vehicle. As this occurs, face plates of adjacent battery modules are made to confront each other, and hence, two face plates result in being provided between battery cells lying at end portions of the adjacent battery modules. Because of this, a sufficient cooling fluid passage cannot be formed between the battery cells lying at the end portions of the battery modules, and hence, the battery cells at the end portions can receive a cooling fluid on only one side thereof. Thus, the cooling of the battery cells lying at the end portions becomes insufficient, compared with the other battery cells in the battery modules which can receive the cooling fluid on both sides thereof.
Consequently, it becomes difficult to maintain a high and uniform battery efficiency of the plurality of battery cells on the basis of battery module by battery module, and the deterioration of one battery cell has resulted in the deterioration of one battery module.